1. Field of the Invention
This invention relates to providing a trailer tire pressure monitoring system. More particularly, this invention concerns a trailer tire pressure monitoring system for warning the driver of a deflating tire on a trailer prior to tire failure. In addition, this invention concerns the provision of a tire pressure monitoring system which is capable of detecting a deflated tire by comparing the rotational speed of several tires.
2. Description of the Prior Art
Typically, vehicle-coupled trailers are used to transport an assortment of cargos such as, for example, goods, livestock, and transient living quarters. Oftentimes, the driver of the towing vehicle will be unaware of the occurrence of air pressure loss in one or more of the trailers tires until it is too late and the tire fails. For single axle trailers comprising only one tire on each side of the trailer, a failure in a single tire may lead to catastrophic consequences, such as trailer rollover or jackknifing, which may not only damage the contents of the trailer but also produce a traffic hazard to other motorists. Even for those single-axle trailers having dual wheels per trailer side, or multi-axle trailers comprising multiple wheels on each side of the trailer, a single tire failure can still result in damage to the trailer as well as collateral damage to other motorists caused by flying tire debris. With these concerns in mind, if a device were utilized to alert the driver of a possible hazardous tire condition, preventive measures may be taken in time to minimize damage to not only the affected tire but also to the remaining trailer components, the trailer body, the tow vehicle, and the general public sharing the road.
The current methods of detecting when a potentially abnormal air pressure condition in a tire may be present typically fall into two categories: direct air pressure detection and indirect air pressure detection. Regarding the first category, direct air pressure detection methods typically involve the use of air pressure detectors within each individual tire which transmit a sensor signal to a receiving unit for processing and interpretation. An example of such a direct air pressure detection system can be found in the U.S. Pat. No. 5,741,966 issued to Handfield et al. which teaches tire pressure monitoring systems in which pressure detection units are disposed within the tire and which sends signals relating to the tire conditions, over an electromagnetic path, to a central receiver unit. Although this system may be adequate for its intended uses despite certain inefficiencies, the fact that signals are sent to the central receiver unit via an electromagnetic path makes this system susceptible to erroneous readings when used on a trailer due to the fact that trailers are often equipped with electric brakes which also generate magnetic fields.
With reference now to the second category, indirect air pressure detection methods typically measure the rotational speed of each tire and compare it with the rotational speed of the remaining measured tires. The theory motivating indirect pressure measurement being that upon losing air pressure, a tire's effective outer diameter decreases, which results in a corresponding increase in the rotational speed of the wheel in order to "keep up" with the land speed of the vehicle. Upon detecting a tire rotating at a higher speed than the remaining tires, the driver is alerted of a possible abnormal tire condition. Those systems which utilize indirect air pressure detection methods typically take advantage of existing hardware which is currently available on passenger vehicles for detecting the rotational speed of wheels. For example, many passenger vehicles are currently equipped with 4 wheel ABS (anti-lock braking system) devices and/or TRC (Traction Control) devices which utilize tire revolution detection-type devices for their respective operations. Examples of systems which utilize existing ABS or TRC hardware can be found in U.S. Pat. Nos. 5,442,331, 5,218,862, and 4,876,528 issued to, respectively, Kishimoto et al., Hurrell, II et al., and Walker et al. Although such systems also may be adequate for their respective intended uses, the fact that trailers typically are not provided with ABS or TRC hardware makes the aforementioned prior art systems unsuited for trailer applications.
Thus, the aforementioned systems and associated methods for monitoring tire pressure for passenger vehicles do not adequately address nor solve the above concerns with respect to trailers.